In the Linux kernel, the following vulnerability has been resolved:
crypto: af_alg - Fix missing initialisation affecting gcm-aes-s390
Fix af_alg_alloc_areq() to initialise areq->first_rsgl.sgl.sgt.sgl to point
to the scatterlist array in areq->first_rsgl.sgl.sgl.
Without this, the gcm-aes-s390 driver will oops when it tries to do
gcm_walk_start() on req->dst because req->dst is set to the value of
areq->first_rsgl.sgl.sgl by _aead_recvmsg() calling
aead_request_set_crypt().
The problem comes if an empty ciphertext is passed: the loop in
af_alg_get_rsgl() just passes straight out and doesn't set areq->first_rsgl
up.
This isn't a problem on x86_64 using gcmaes_crypt_by_sg() because, as far
as I can tell, that ignores req->dst and only uses req->src[*].
[*] Is this a bug in aesni-intel_glue.c?
The s390x oops looks something like:
Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 0000000a00000000 TEID: 0000000a00000803
Fault in home space mode while using kernel ASCE.
AS:00000000a43a0007 R3:0000000000000024
Oops: 003b ilc:2 [#1] SMP
...
Call Trace:
[<000003ff7fc3d47e>] gcm_walk_start+0x16/0x28 [aes_s390]
[<00000000a2a342f2>] crypto_aead_decrypt+0x9a/0xb8
[<00000000a2a60888>] aead_recvmsg+0x478/0x698
[<00000000a2e519a0>] sock_recvmsg+0x70/0xb0
[<00000000a2e51a56>] sock_read_iter+0x76/0xa0
[<00000000a273e066>] vfs_read+0x26e/0x2a8
[<00000000a273e8c4>] ksys_read+0xbc/0x100
[<00000000a311d808>] __do_syscall+0x1d0/0x1f8
[<00000000a312ff30>] system_call+0x70/0x98
Last Breaking-Event-Address:
[<000003ff7fc3e6b4>] gcm_aes_crypt+0x104/0xa68 [aes_s390]
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it