CVE-2026-53176: Linux kernel · IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 9.8 Critical · fixed in e8a013c0c3ca2f6708341a56612a3f6d6921620a : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 13:47 UTC
- EPSS
- 0.7% chance of exploitation in 30 days – higher than 55% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers can reliably automate steps 1–4 of the kill chain
- Technical impact
- Total control over the software or total information disclosure
CISA SSVC assessment, 2026-10-16.
- Patch
- Available – fixed in e8a013c0c3ca2f6708341a56612a3f6d6921620a, df422fd273c96c2ee5beb80fc21adc8c70c29260, c1234229399f4af12c553b1b0ffd978eeba65548 +5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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Description
In the Linux kernel, the following vulnerability has been resolved: IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN In drivers/infiniband/ulp/isert/ib_isert.c, isert_login_recv_done() computes the login request payload length as wc->byte_len minus ISER_HEADERS_LEN with no lower bound, and login_req_len is a signed int. A remote iSER initiator can post a login Send work request carrying fewer than ISER_HEADERS_LEN (76) bytes, so the subtraction underflows and login_req_len becomes negative. isert_rx_login_req() then reads that negative length back into a signed int, takes size = min(rx_buflen, MAX_KEY_VALUE_PAIRS), and because the min() is signed it keeps the negative value; the value is then passed as the memcpy() length and sign-extended to a multi-gigabyte size_t. The copy into the 8192-byte login->req_buf runs far out of bounds and faults, crashing the target node. The login phase precedes iSCSI authentication, so no credentials are required to reach this path. Reject any login PDU shorter than ISER_HEADERS_LEN before the subtraction, mirroring the existing early return on a failed work completion, so login_req_len can never go negative. The upper bound was already safe: a posted login buffer cannot deliver more than ISER_RX_PAYLOAD_SIZE, so the difference stays at or below MAX_KEY_VALUE_PAIRS and the existing min() clamps it; only the missing lower bound needs to be added.
References
- git.kernel.org/stable/c/75ee6e4aa096aa9e7b2dd5c8ff98356e30aceefb (opens in a new tab)
- git.kernel.org/stable/c/e8a013c0c3ca2f6708341a56612a3f6d6921620a (opens in a new tab)
- git.kernel.org/stable/c/bd22740d7f14cb1c0289444cfd2c8d2938667c1d (opens in a new tab)
- git.kernel.org/stable/c/c1234229399f4af12c553b1b0ffd978eeba65548 (opens in a new tab)
- git.kernel.org/stable/c/c5584e089b5af7b3bf8bd5e8ca0560cbf32b0a47 (opens in a new tab)
- git.kernel.org/stable/c/df422fd273c96c2ee5beb80fc21adc8c70c29260 (opens in a new tab)
- git.kernel.org/stable/c/1ca40b243277c9e88be5e00bd3e083f71aefb93e (opens in a new tab)
- git.kernel.org/stable/c/29e7b925ae6df64894e82ab6419994dc25580a8a (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-53176 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2492741 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53176.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:68507 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:68570 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:68531 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:68532 (opens in a new tab)