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mbedTLS 3.6.6 TLS 1.3: Heap corruption issue

by Sielatchom, Cesaire

Hello, while setting up a TLS 1.3 client based on mbedTLS 3.6.6, I am facing a memory corruption issue and would appreciate any advice on how to debug it further. Initial symptoms ================ Originally I was using FreeRTOS heap_4 as the allocator. During the TLS handshake I eventually hit one of the following assertions inside the FreeRTOS heap implementation: configASSERT( heapBLOCK_IS_ALLOCATED( pxLink ) != 0 ); configASSERT( pxLink->pxNextFreeBlock == heapPROTECT_BLOCK_POINTER( NULL ) ); This suggested corruption of the heap block header structures. Isolation attempt ================= To exclude interactions with the FreeRTOS heap allocator, I reconfigured mbedTLS to use a dedicated static memory pool by enabling: MBEDTLS_MEMORY_BUFFER_ALLOC_C I allocated a dedicated 1 MB memory pool located in external RAM and initialized it via: mbedtls_memory_buffer_alloc_init(...); No other software component is intended to access this memory area. New failure =========== With the dedicated memory pool in place, the TLS 1.3 handshake now fails inside memory_buffer_alloc.c with the following consistency check: if (cur->alloc != 0) { #if defined(MBEDTLS_MEMORY_DEBUG) mbedtls_fprintf(stderr, "FATAL: block in free_list but allocated data\n"); #endif mbedtls_exit(1); } The execution stops with: FATAL: block in free_list but allocated data This appears to indicate that a block found in the free list still has its allocation flag set. What I have checked so far ========================== - Initially I suspected FreeRTOS heap corruption. - I added hardware watchpoints at the beginning and end of the affected memory blocks. - No obvious buffer overflow was detected using those watchpoints. - Secure and Non-Secure heaps are separated. - I experimented with MPU guard regions. - The issue is reproducible under TLS/WebSocket traffic. - mbedTLS is now running from a dedicated static memory pool. - The dedicated mbedTLS pool is approximately 1 MB and is not shared with the FreeRTOS heap. Platform ======== - STM32U585 - TrustZone enabled - FreeRTOS - mbedTLS 3.6.6 - TLS 1.3 enabled - WebSocket over TLS Are there recommended debugging options or allocator diagnostics that could help identify the offending allocation or the block whose metadata became inconsistent? Has anyone experienced similar issues specifically with TLS 1.3 handshakes, especially during key share generation? Relevant handshake log ====================== init connect[1] . Performing the SSL/TLS handshake...[TLS][2] ../SRV_TLS/mbedtls/library/ssl_tls.c:4670: => handshake [TLS][2] ../SRV_TLS/mbedtls/library/ssl_msg.c:2356: => flush output [TLS][2] ../SRV_TLS/mbedtls/library/ssl_msg.c:2365: <= flush output [TLS][2] ../SRV_TLS/mbedtls/library/ssl_tls.c:4589: client state: MBEDTLS_SSL_HELLO_REQUEST [TLS][3] ../SRV_TLS/mbedtls/library/ssl_misc.h:1353: handshake state: 0 (MBEDTLS_SSL_HELLO_REQUEST) -> 1 (MBEDTLS_SSL_CLIENT_HELLO) [TLS][2] ../SRV_TLS/mbedtls/library/ssl_msg.c:2356: => flush output [TLS][2] ../SRV_TLS/mbedtls/library/ssl_msg.c:2365: <= flush output [TLS][2] ../SRV_TLS/mbedtls/library/ssl_tls.c:4589: client state: MBEDTLS_SSL_CLIENT_HELLO [TLS][2] ../SRV_TLS/mbedtls/library/ssl_client.c:921: => write client hello [TLS][3] ../SRV_TLS/mbedtls/library/ssl_client.c:487: dumping 'client hello, random bytes' (32 bytes) [TLS][3] ../SRV_TLS/mbedtls/library/ssl_client.c:487: 0000: 9a 99 37 69 fa 5e 07 f7 ff c8 5b ac 56 fe 45 1a ..7i.^....[.V.E. [TLS][3] ../SRV_TLS/mbedtls/library/ssl_client.c:487: 0010: 53 d1 a1 d6 27 f6 5d 5a 4e 5b 2a 80 4c 1e 9b cb S...'.]ZN[*.L... [TLS][3] ../SRV_TLS/mbedtls/library/ssl_client.c:512: dumping 'session id' (0 bytes) [TLS][3] ../SRV_TLS/mbedtls/library/ssl_client.c:370: client hello, add ciphersuite: 1301, TLS1-3-AES-128-GCM-SHA256 [TLS][3] ../SRV_TLS/mbedtls/library/ssl_client.c:388: adding EMPTY_RENEGOTIATION_INFO_SCSV [TLS][3] ../SRV_TLS/mbedtls/library/ssl_client.c:397: client hello, got zu cipher suites [TLS][3] ../SRV_TLS/mbedtls/library/ssl_tls13_client.c:57: client hello, adding supported versions extension [TLS][3] ../SRV_TLS/mbedtls/library/ssl_tls13_client.c:80: supported version: [3:4] [TLS][3] ../SRV_TLS/mbedtls/library/ssl_tls13_client.c:86: supported version: [3:3] [TLS][3] ../SRV_TLS/mbedtls/library/ssl_tls13_client.c:573: no cookie to send; skip extension [TLS][3] ../SRV_TLS/mbedtls/library/ssl_tls13_client.c:285: client hello: adding key share extension [TLS][1] ../SRV_TLS/mbedtls/library/ssl_tls13_generic.c:1552: Perform PSA-based ECDH/FFDH computation. FATAL: block in free_list but allocated data Any suggestions, debugging techniques, or similar experiences would be greatly appreciated. Thank you very much. Best regards, Cesaire Mit freundlichen Grüßen / Best regards i. A. Cesaire Sielatchom Konstrukteur und Entwickler [BKS_4c.gif] BKS GmbH Entwicklung Elektronik Heidestr. 71 D-42549 Velbert Telefon +49 2051 201 528<tel:+49%202051%20201%20528> Cesaire.Sielatchom(a)bks.de<mailto:Cesaire.Sielatchom@bks.de> www.bks.de<https://www.bks.de/de-de> BKS GmbH Sitz der Gesellschaft: Velbert Amtsgericht Wuppertal, HRB 17711 GF: Thomas Polonyi Vorsitzender des Aufsichtsrats: Dirk Leuker WEEE-Reg.-Nr. DE 14737171 [Email_Footer SicherheitsExpo 2026.jpg] Diese Mail ist vertraulich. Wenn Sie nicht der beabsichtigte Empfänger sind, dürfen Sie die Informationen nicht offenlegen, benutzen, kopieren oder verteilen. Wenn Sie diese Mail durch einen Fehler bekommen haben, teilen Sie uns dies bitte dadurch mit, dass Sie diese Mail an den Absender zurückschicken. Bitte löschen Sie danach diese Mail und alle Anhänge. Danke. This e-mail message including any attachment is intended for the sole use of the individual or entity named above. If you are not the intended recipient, please do not read, copy, use or disclose this communication to others; also please notify the sender by replying to this message and then delete it and all attachments from your system.Thank you.

5 hours, 31 minutes

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Updated invitation with note: MBed-TLS Technical Forum - Asia @ Every 4 weeks from 10am to 10:50am on Monday (GMT) (mbed-tls@lists.trustedfirmware.org)

by Shaun Longhorn

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1 day, 6 hours

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Synced invitation: MBed-TLS Technical Forum - Asia @ Every 4 weeks from 10am to 10:50am on Monday (BST) (mbed-tls@lists.trustedfirmware.org)

by Shaun Longhorn

This email keeps the event up to date in your calendar. MBed-TLS Technical Forum - Asia Every 4 weeks from 10am to 10:50am on Monday United Kingdom Time Location https://linaro-org.zoom.us/j/97758661706?pwd=baMjUvnWbY20z3ignQca7QVahhozkI… https://www.google.com/url?q=https%3A%2F%2Flinaro-org.zoom.us%2Fj%2F9775866… Trusted Firmware is inviting you to a scheduled Zoom meeting.Topic: MBed-TLS Technical Forum - AsiaTime: Jun 16, 2025 10:00 AM London Every 4 weeks on Mon, 39 occurrence(s)Please download and import the following iCalendar (.ics) files to your calendar system.Weekly: https://linaro-org.zoom.us/meeting/tJMqcuGuqDotGtIbACm498ytl0ZhydWKdu1b/ics… Zoom Meetinghttps://linaro-org.zoom.us/j/97758661706?pwd=baMjUvnWbY20z3ignQca7QVahhozkI.1Meeting ID: 977 5866 1706Passcode: 577208---One tap mobile+16892781000,,97758661706# US+17193594580,,97758661706# US---Dial by your location• +1 689 278 1000 US• +1 719 359 4580 US• +1 253 205 0468 US• +1 253 215 8782 US (Tacoma)• +1 301 715 8592 US (Washington DC)• +1 305 224 1968 US• +1 309 205 3325 US• +1 312 626 6799 US (Chicago)• +1 346 248 7799 US (Houston)• +1 360 209 5623 US• +1 386 347 5053 US• +1 507 473 4847 US• +1 564 217 2000 US• +1 646 558 8656 US (New York)• +1 646 931 3860 US• +1 669 444 9171 US• +1 669 900 9128 US (San Jose)• 833 548 0282 US Toll-free• 833 928 4608 US Toll-free• 833 928 4609 US Toll-free• 833 928 4610 US Toll-free• 877 853 5247 US Toll-free• 888 788 0099 US Toll-free• 833 548 0276 US Toll-freeMeeting ID: 977 5866 1706Find your local number: https://linaro-org.zoom.us/u/acdtApJNbc Guests mbed-tls(a)lists.trustedfirmware.org psa-crypto(a)lists.trustedfirmware.org ~~//~~ Invitation from Google Calendar: https://calendar.google.com/calendar/ You are receiving this email because you are an attendee on the event. Forwarding this invitation could allow any recipient to send a response to the organizer, be added to the guest list, invite others regardless of their own invitation status, or modify your RSVP. Learn more https://support.google.com/calendar/answer/37135#forwarding

1 day, 6 hours

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Updated invitation with note: MBed TLS Technical Forum - US @ Every 4 weeks from 4:30pm to 5:30pm on Monday (BST) (mbed-tls@lists.trustedfirmware.org)

by Shaun Longhorn

This event has been updated with a note: "Pushing to fix meeting link issue" Changed: location MBed TLS Technical Forum - US Every 4 weeks from 4:30pm to 5:30pm on Monday United Kingdom Time Location https://linaro-org.zoom.us/j/93546216467?pwd=ja9Nxd0uLBn04jg1Be0NTy17Konzfl… https://www.google.com/url?q=https%3A%2F%2Flinaro-org.zoom.us%2Fj%2F9354621… Trusted Firmware is inviting you to a scheduled Zoom meeting.Topic: MBed TLS Technical Forum - USTime: May 4, 2026 04:30 PM LondonEvery 4 weeks on Mon, 38 occurrence(s)Please download and import the following iCalendar (.ics) files to your calendar system.Weekly: https://linaro-org.zoom.us/meeting/tJcoc--qrz0uHNNmuZMtfpylBgIZjC2so7xz/ics… Zoom Meetinghttps://linaro-org.zoom.us/j/93546216467?pwd=ja9Nxd0uLBn04jg1Be0NTy17Konzfl.1Meeting ID: 935 4621 6467Passcode: 683772---One tap mobile+13126266799,,93546216467# US (Chicago)+13462487799,,93546216467# US (Houston)---Dial by your location• +1 312 626 6799 US (Chicago)• +1 346 248 7799 US (Houston)• +1 360 209 5623 US• +1 386 347 5053 US• +1 507 473 4847 US• +1 564 217 2000 US• +1 646 558 8656 US (New York)• +1 646 931 3860 US• +1 669 444 9171 US• +1 669 900 9128 US (San Jose)• +1 689 278 1000 US• +1 719 359 4580 US• +1 253 205 0468 US• +1 253 215 8782 US (Tacoma)• +1 301 715 8592 US (Washington DC)• +1 305 224 1968 US• +1 309 205 3325 US• 833 928 4609 US Toll-free• 833 928 4610 US Toll-free• 877 853 5247 US Toll-free• 888 788 0099 US Toll-free• 833 548 0276 US Toll-free• 833 548 0282 US Toll-free• 833 928 4608 US Toll-freeMeeting ID: 935 4621 6467Find your local number:https://linaro-org.zoom.us/u/azKzC20VI Guests psa-crypto(a)lists.trustedfirmware.org mbed-tls(a)lists.trustedfirmware.org hordijk(a)aurora.tech Ben Taylor cjej65eug(a)gmail.com View all guest info https://calendar.google.com/calendar/event?action=VIEW&eid=dm9wcGhnbnZvMnRh… Reply for mbed-tls(a)lists.trustedfirmware.org and view more details https://calendar.google.com/calendar/event?action=VIEW&eid=dm9wcGhnbnZvMnRh… Your attendance is optional. ~~//~~ Invitation from Google Calendar: https://calendar.google.com/calendar/ You are receiving this email because you are an attendee on the event. Forwarding this invitation could allow any recipient to send a response to the organizer, be added to the guest list, invite others regardless of their own invitation status, or modify your RSVP. Learn more https://support.google.com/calendar/answer/37135#forwarding

1 day, 6 hours

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extract AKI info from cert via mbedtls ?

by Danny Backx

Hi, How can I extract the AKI (Authority Key Identifier) from a certificate using mbedtls ? I could parse the certificate file itself, I guess, but isn't that what mbedtls does? Thanks, Danny https://www.rfc-editor.org/info/rfc5280#section-4.2.1.1 -- Danny Backx - dannybackx(a)telenet.be

1 week, 4 days

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Proposal to unify tf.org vulnerability referencing in NVD

by sandrine.afsa＠arm.com

The content of this message was lost. It was probably cross-posted to multiple lists and previously handled on another list.

3 weeks, 5 days

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CI infrastructure scheduled maintenance: 4th June Sep 2026

by Saheer Babu

Hi all, We will be upgrading Cloudbees CI and clusters hosting review.trustedfirmware.org and ci.trustedfirmware.org on Wednesday, 3rd June 2025 at 16:00 GMT+1. During this maintenance window, both services will be unavailable for approximately 8 hours. A follow-up email will be sent once the services are fully restored. Best regards, Saheer [LOGO SMALL] Saheer Babu Principal Software Engineer CESW – Engineering Infrastructure

4 weeks

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need help migrating to mbedtls 4.0 (esp32)

by Danny Backx

I got into trouble with migrating to the latest (v6.0) version of esp-idf, because it implies a migration to mbedtls 4.0. I had a working application (library really) to obtain ACME certificates from letsencrypt.org. I tried porting, but ran into trouble. So please help. To debug, I try to mimic the example in Appendix A.2 of RFC 7515. Where this should obviously succeed, the current output I get is : I (12:57:46.067) main_task: Calling app_main() I (12:57:46.088) Crypto: Acme standalone client example © 2026 by Danny Backx I (12:57:46.089) Crypto: checkRfc7515_a21 Base64({"alg":"RS256"}) -> eyJhbGciOiJSUzI1NiJ9 is correct I (12:57:46.094) Crypto: checkRfc7515_a21 Base64({"iss":"joe", "exp":1300819380, "http://example.com/is_root":true}) -> eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ is correct I (12:57:46.121) Crypto: checkRfc7515_a21 importPrivateKey() -> 1073741825 E (12:57:46.122) psa_crypto: psa_get_and_lock_key_slot_with_policy psa_key_policy_permits -> -133 E (12:57:46.129) psa_crypto: psa_sign_internal psa_get_and_lock_key_slot_with_policy -> -133 E (12:57:46.137) Crypto: psa_sign_hash (key 1073741825) failed (not permitted, -133 0x0085) I (12:57:46.145) Crypto: checkRfc7515_a21 Signature(eyJhbGciOiJSUzI1NiJ9,eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ) -> (null) E (12:57:46.161) Crypto: Signature 0, fail E (12:57:46.165) Crypto: RFC 7515 A.2.1 : validation failed Some of the "psa_crypto" lines come from debug statements I added in the library. The whole source for this is in one file at https://sourceforge.net/p/esp32-acme-client/code/HEAD/tree/trunk/examples/s… . Obviously it's the hashing step which I had under control with a previous library which I don't call correctly (or I don't know how to import the right key). What am I doing wrong ? Thanks, Danny -- Danny Backx - dannybackx(a)telenet.be

1 month, 1 week

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mbedtls_ssl_read() return code MBEDTLS_ERR_SSL_RECEIVED_NEW_SESSION_TICKET

by Fabian Keil

I'm currently working on adding MbedTLS 4.x support for Privoxy [0] and noticed that mbedtls_ssl_read() frequently returns MBEDTLS_ERR_SSL_RECEIVED_NEW_SESSION_TICKET. Apparently the error code was added in f8a4994ec7 and marked experimental in da13072c5b. It doesn't seem explicitly documented at [1], but of course it's covered by "or another negative error code". My current solution is to simply continue reading: extern int ssl_recv_data(struct ssl_attr *ssl_attr, unsigned char *buf, size_t max_length) { [...] do { ret = mbedtls_ssl_read(ssl, buf, max_length); #if MBEDTLS_VERSION_MAJOR > 3 if (ret == MBEDTLS_ERR_SSL_RECEIVED_NEW_SESSION_TICKET) { log_error(LOG_LEVEL_CONNECT, "mbedtls_ssl_read() reported new session ticket for " "the connection on socket %d.", ssl_attr->mbedtls_attr.socket_fd.fd); } #endif } while (ret == MBEDTLS_ERR_SSL_WANT_READ #if MBEDTLS_VERSION_MAJOR > 3 || ret == MBEDTLS_ERR_SSL_RECEIVED_NEW_SESSION_TICKET #endif || ret == MBEDTLS_ERR_SSL_WANT_WRITE); When using MbedTLS 4.1.0 on ElectroBSD 14.4-STABLE this seems to work. For some connections the log message is emitted once, for others it's emitted twice: 09:20:58.982 024 Connect: Connected to 127.0.1.2[127.0.1.2]:9050. 09:20:59.222 024 Connect: Created new connection to www.electrobsd.org:443 on socket 9. 09:20:59.243 024 Connect: Performing the TLS handshake with the server. 09:20:59.583 024 Connect: Server successfully connected over TLSv1.3 (TLS1-3-CHACHA20-POLY1305-SHA256). 09:20:59.583 024 Connect: Encrypted request sent. 09:20:59.809 024 Connect: mbedtls_ssl_read() reported new session ticket for the connection on socket 9. 09:20:59.902 024 Connect: mbedtls_ssl_read() reported new session ticket for the connection on socket 9. 09:21:00.041 024 Header: scan: HTTP/1.1 200 OK I noticed that there's already an open ticket [2] which contains the sentence: | For client side, mbedtls_ssl_{read,write} might return the error also, | we should process it in the error handler also. I haven't seen mbedtls_ssl_write() return MBEDTLS_ERR_SSL_RECEIVED_NEW_SESSION_TICKET yet, though. Can you confirm that handling MBEDTLS_ERR_SSL_RECEIVED_NEW_SESSION_TICKET by continuing reading is currently the best option? Thanks. Fabian [0]: <https://www.privoxy.org/> [1]: <https://os.mbed.com/teams/sandbox/code/mbedtls/docs/tip/ssl_8h.html#aa2c29e…> [2]: <https://github.com/Mbed-TLS/mbedtls/issues/6640>

2 months, 1 week

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Could anyone please handle this PR?

by Elsa zz

Hi, Could anyone please handle this PR? Fix build warning/error using llvm-mingw: - https://github.com/Mbed-TLS/mbedtls/pull/10695 Thanks!

2 months, 2 weeks

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