Amazon Linux 2 (EOS) Security Advisory: ALAS2OPENSSL-SNAPSAFE-2026-012
Advisory Released Date: 2026-09-14
Advisory Updated Date: 2026-09-14
Issue summary: Receiving a DTLS record for a future epoch while a handshake
is in progress causes OpenSSL to buffer far more memory than the record
itself requires.
Impact summary: A peer can use a small amount of network traffic to make an
OpenSSL DTLS endpoint retain a disproportionately large amount of memory,
which may lead to a Denial of Service.
CWE: CWE-405: Asymmetric Resource Consumption (Amplification)
Description: While a DTLS handshake is in progress, a peer may legitimately
have already moved on to the next epoch (for example, having sent its
ChangeCipherSpec and Finished messages) before the local endpoint has
processed the same transition, typically because of reordering on the
underlying UDP transport. OpenSSL buffers such early records so that they
can be processed once the local endpoint catches up.
Buffering a record currently retains the entire read buffer it arrived in,
which is sized to hold the largest possible DTLS record (around 16
kilobytes), rather than just the bytes that make up the record itself. Up
to 100 such records may be buffered per connection. As a result, a peer
that sends a stream of small forged records claiming to belong to the next
epoch can cause an OpenSSL DTLS endpoint to retain around 1.7 megabytes of
memory, despite sending only a small fraction of that amount of data over
the network.
An attacker therefore gains a memory amplification factor of around 1200,
and can multiply the effect across as many associations as it is able to
open, making this a remote memory exhaustion Denial of Service risk for
DTLS servers. Since the memory retained per connection remains bounded,
and any limit an application already places on the number of concurrent
associations also bounds the total exposure, this issue has been assessed
as Low severity.
FIPS impact: no
No FIPS modules are affected by this issue as the affected code is outside
the OpenSSL FIPS module boundary.
OpenSSL 4.0, 3.6, 3.5, 3.4, 3.0, 1.1.1 and 1.0.2 are vulnerable to this
issue.
OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.
Premium support customers only:
OpenSSL 1.1.1 users should upgrade to OpenSSL 1.1.1zi
OpenSSL 1.0.2 users should upgrade to OpenSSL 1.0.2zr
This issue was reported on 18 May 2026 by Amazon Web Services.
The fix has been developed by Matt Caswell.
-- cut (non-publishing metadata for internal use) --
Reported by: Amazon Web Services
Fixed by: Matt Caswell (CVE-2026-54874)
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. (CVE-2026-63072)
Affected Packages:
openssl-snapsafe
Note:
This advisory is applicable to Amazon Linux 2 - Openssl-snapsafe Extra. Visit this page to learn more about Amazon Linux 2 (AL2) Extras and this FAQ section for the difference between AL2 Core and AL2 Extras advisories.
Issue Correction:
Run yum update openssl-snapsafe or yum update --advisory ALAS2OPENSSL-SNAPSAFE-2026-012 to update your system.
aarch64:
openssl-snapsafe-1.0.2k-24.amzn2.0.22.aarch64
openssl-snapsafe-libs-1.0.2k-24.amzn2.0.22.aarch64
openssl-snapsafe-devel-1.0.2k-24.amzn2.0.22.aarch64
openssl-snapsafe-static-1.0.2k-24.amzn2.0.22.aarch64
openssl-snapsafe-perl-1.0.2k-24.amzn2.0.22.aarch64
openssl-snapsafe-debuginfo-1.0.2k-24.amzn2.0.22.aarch64
i686:
openssl-snapsafe-1.0.2k-24.amzn2.0.22.i686
openssl-snapsafe-libs-1.0.2k-24.amzn2.0.22.i686
openssl-snapsafe-devel-1.0.2k-24.amzn2.0.22.i686
openssl-snapsafe-static-1.0.2k-24.amzn2.0.22.i686
openssl-snapsafe-perl-1.0.2k-24.amzn2.0.22.i686
openssl-snapsafe-debuginfo-1.0.2k-24.amzn2.0.22.i686
src:
openssl-snapsafe-1.0.2k-24.amzn2.0.22.src
x86_64:
openssl-snapsafe-1.0.2k-24.amzn2.0.22.x86_64
openssl-snapsafe-libs-1.0.2k-24.amzn2.0.22.x86_64
openssl-snapsafe-devel-1.0.2k-24.amzn2.0.22.x86_64
openssl-snapsafe-static-1.0.2k-24.amzn2.0.22.x86_64
openssl-snapsafe-perl-1.0.2k-24.amzn2.0.22.x86_64
openssl-snapsafe-debuginfo-1.0.2k-24.amzn2.0.22.x86_64