CVE-2026-87044
MediumCVSS 6.5Exploitation Probability (EPSS)
Low risk11th percentile - higher than 11% of all known CVEs
Summary
In the Mbed TLS crypto shim driver (drivers/crypto/crypto_mbedtls_shim.c), error paths in mbedtls_cbc() and mbedtls_aead() after a successful psa_cipher_encrypt_setup()/psa_aead_decrypt_setup() return without calling psa_cipher_abort()/psa_aead_abort(). This permanently leaks the heap-allocated mbedtls_aes_context (about 288 bytes) from Mbed TLS's fixed static heap (default 512 bytes) on each failed operation. An unauthenticated attacker can exhaust the heap by sending 802.15.4 frames with a bogus MIC or via the OSDP channel, permanently breaking subsequent cryptographic operations until reboot.
Risk Assessment
Exhausting the Mbed TLS heap permanently breaks all cryptographic operations in the image, including link-layer security and any TLS/DTLS sharing the heap, resulting in denial of service until the device is rebooted. There is no memory corruption or information disclosure; the impact is limited to availability.
Recommendation
Update to a version containing the fix that routes all post-setup failures in mbedtls_cbc() and mbedtls_aead() through a common error label calling the matching PSA abort. Until patched, limit 802.15.4 radio exposure and OSDP channels, and monitor device reboots.
Other vulnerabilities in Mbed TLS
See all- CVE-2026-34877Critical
A vulnerability in Mbed TLS (versions 2.19.0 to 3.6.5 and 4.0.0) is caused by insufficient protection of serialized SSL structures. An attacker can modify these structures, leading to memory corruption and potential arbitrary code execution.
- CVE-2026-73064Low
In Mbed TLS 3.2.0 through 3.6.6 and 4.0.0 through 4.1.0, an attacker who can cause an entropy source to fail can remove or inject bytes into the start of the TLS stream. This only affects TLS 1.3 servers.
- CVE-2026-25832Low
In Mbed TLS 3.6.x before 3.6.7 and 4.1.x before 4.1.2, the TLS 1.3 client accepts a HelloRetryRequest selecting a group that was not advertised. This can violate TLS 1.3 protocol negotiation expectations.
- CVE-2026-34876High
Mbed TLS 3.x before 3.6.6 has an out-of-bounds read vulnerability in mbedtls_ccm_finish() due to missing validation of the tag_len parameter. An attacker can obtain adjacent CCM context data.
- CVE-2025-66442Medium
In Mbed TLS through 4.0.0, a compiler-induced timing side channel (in RSA and CBC/ECB decryption) occurs only with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- CVE-2025-59438Medium
Mbed TLS through 3.6.4 has an Observable Timing Discrepancy vulnerability. This may allow an attacker to infer information based on timing differences in cryptographic operations.
- CVE-2025-54764Medium
Mbed TLS before 3.6.5 allows a local timing attack against certain RSA operations, and direct calls to mbedtls_mpi_mod_inv or mbedtls_mpi_gcd. An attacker with local access may exploit timing differences to extract information about cryptographic operations.
Original NVD description (English source)
The Mbed TLS crypto shim driver in drivers/crypto/crypto_mbedtls_shim.c drives PSA multipart cipher and AEAD operations. In mbedtls_cbc() and mbedtls_aead(), every error path after a successful psa_cipher_encrypt_setup() / psa_aead_decrypt_setup() returned directly without calling psa_cipher_abort() / psa_aead_abort(). Because the abort is the only thing that reaches mbedtls_cipher_free(), each failed operation permanently leaked the heap-allocated mbedtls_aes_context (roughly 288 bytes) that setup had allocated from Mbed TLS's fixed static heap (_mbedtls_heap[CONFIG_MBEDTLS_HEAP_SIZE], default 512 bytes). With CONFIG_PSA_CRYPTO_PROVIDER_TFM the leaked object is instead a finite secure-partition multipart-operation slot. The failure is chosen by an unauthenticated attacker. With CONFIG_NET_L2_IEEE802154_SECURITY backed by this driver, ieee802154_decrypt_auth() in subsys/net/l2/ieee802154/ieee802154_security.c invokes cipher_ccm_op() on every received secured frame, with no authentication ahead of the MIC check. A device in radio range can transmit a stream of syntactically valid 802.15.4 frames carrying a bogus MIC; each one makes psa_aead_verify() fail and leaks a block. The CBC path is reachable the same way through the OSDP secure channel, where CONFIG_OSDP_SC_ENABLED selects this shim and osdp_encrypt() / osdp_decrypt() leave out_buf_max unset, so every operation fails inside psa_cipher_update(). Exhausting the Mbed TLS heap — which the default configuration reaches after a couple of failed operations, and any realistic configuration reaches in well under a second of frames — makes all subsequent mbedtls_calloc() calls fail. Every later cryptographic operation in the image then fails permanently, including link-layer security and any TLS/DTLS sharing the same heap, until the device is rebooted. There is no memory corruption or information disclosure: frames with an invalid MIC are still rejected, so the impact is limited to availability. The fix routes all post-setup failures in mbedtls_cbc() and mbedtls_aead() through a common error: label that calls the matching PSA abort before returning. Setup failures need no change, since the PSA core aborts the operation itself when setup fails.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS