CVE-2026-63072 Heap Buffer Overflow in CMS Key Unwrapping
An attacker can cause a denial of service by sending a crafted CMS message that triggers an 8-byte heap buffer overflow during decryption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63072?
CVE-2026-63072 is a high-severity memory corruption vulnerability in Openssl Openssl, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based on querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive can write and cleanse more bytes than that query reports, causing an 8-byte out-of-bounds heap write.
Impact summary: An attacker who supplies a crafted CMS message can trigger a deterministic 8-byte out-of-bounds heap write when the victim decrypts it with CMS_decrypt(), corrupting the heap and typically resulting in a Denial of Service.
CWE: CWE-787: Out-of-bounds Write
Description: The key-wrap OID is potentially attacker-controlled on the wire. CMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers. An attacker can take a legitimate message and change a single OID byte to select the padded variant while leaving the message otherwise valid. Since the unwrap key is derived from the recipient's private operation (ECDH key agreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot pass, and the decryption fails with integrity failure.
The write is a fixed-size (8-byte), fixed-value (zero) heap overflow immediately past the allocation, requires no special configuration, and is reachable from the public CMS_decrypt() function. The consequence is a heap corruption leading to a Denial of Service. The fix in the CMS code sizes the unwrap output buffer for the worst case so a failed unwrap cannot write past the allocation.
FIPS impact: no
As the CMS code lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.
Weakness: CWE-787
Which versions are affected by CVE-2026-63072?
It affects 1 product.
Linux distribution packages (8)
openvox-agent Red Hat:rhel_satellite_openvox:6::el10 | All versions | 0:8.30.0-1.el10sat |
openvox-agent Red Hat:rhel_satellite_openvox:6::el7 | All versions | 0:8.30.0-1.el7sat |
openvox-agent Red Hat:rhel_satellite_openvox:6::el8 | All versions | 0:8.30.0-1.el8sat |
openvox-agent Red Hat:rhel_satellite_openvox:6::el9 | All versions | 0:8.30.0-1.el9sat |
openssl-1_1-livepatches SUSE:Linux Enterprise Live Patching 15 SP4 | All versions | 0.8-150400.3.26.1 |
openssl-1_1-livepatches SUSE:Linux Enterprise Live Patching 15 SP5 | All versions | 0.8-150500.6.17.1 |
openssl-1_1-livepatches SUSE:Linux Enterprise Live Patching 15 SP6 | All versions | 0.8-150600.11.9.1 |
openssl-1_1-livepatches SUSE:Linux Enterprise Live Patching 15 SP7 | All versions | 0.8-150700.13.12.1 |
Products include Openssl Openssl.
How do I fix CVE-2026-63072?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-63072 being exploited?
There is no known exploitation of CVE-2026-63072 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in Openssl Openssl
Sources
Also known as ALPINE-CVE-2026-63072, AZL-97665, AZL-97890, AZL-97947, BELL-CVE-2026-63072, CLEANSTART-2026-VK14120 and 18 more.