EUVD-2026-64548
GHSA-g4xp-j3j4-vmrq
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Remote TLS peer triggers it (AV:N/PR:N) but only under the non-default TLS_RX_EXPECT_NO_PAD config (AC:H); impact is misplaced writes into the app's own iovec buffers - integrity high, limited disclosure and disruption.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
tls: rx: restore msg_iter before TLS 1.3 optimistic retry
tls_decrypt_sg() advances msg->msg_iter when it maps user pages for the optimistic TLS 1.3 zero-copy path. If the decrypted record turns out not to be unpadded application data, tls_decrypt_sw() retries into a kernel skb, but leaves the iterator advanced.
The subsequent copy from the skb then writes decrypted bytes again at a later point in the caller iovecs while recvmsg() reports only the post-retry length. A TLS peer can trigger this after the receiver enables TLS_RX_EXPECT_NO_PAD.
Revert the iterator by the number of bytes consumed by the optimistic mapping before retrying without zero-copy.
Add a selftest which sends a TLS 1.3 control record with TLS_RX_EXPECT_NO_PAD enabled and verifies that recvmsg() does not overwrite later iovecs beyond the returned length.
AnalysisAI
Improper handling of the receive-side message iterator in the Linux kernel's kernel-TLS (kTLS) subsystem lets a remote TLS peer cause recvmsg() to write decrypted bytes into the wrong offsets of a receiver's user-space iovec buffers. When the optimistic TLS 1.3 zero-copy path maps user pages and then falls back to a kernel skb, the iterator is left advanced, so bytes are written a second time past the length recvmsg() reports. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the receiving socket to have kernel-TLS (kTLS) receive offload active on a TLS 1.3 connection AND to have explicitly enabled the TLS_RX_EXPECT_NO_PAD socket option - this is the exact configuration named in the description and is not the default. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The published CVSS 9.8 (AV:N/AC:L/PR:N/UI:N/C:H/I:H/A:H) substantially overstates real-world risk and appears to be a default maximal kernel scoring. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A receiving application enables kernel-TLS with TLS_RX_EXPECT_NO_PAD on a TLS 1.3 connection and calls recvmsg() with a multi-segment iovec. A malicious or malfunctioning TLS peer sends a crafted control-type record that triggers the optimistic zero-copy decrypt followed by the kernel-skb retry; the leftover-advanced iterator causes decrypted bytes to be written past the returned length into later iovec segments, corrupting or leaking data the application did not expect to receive. … |
| Remediation | Vendor-released patch: update to Linux stable 6.18.45, 7.1.9, or 7.2 (or later), which apply the fix that reverts msg_iter before the non-zero-copy retry (mainline commit 3c837266a734). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify systems with TLS_RX_EXPECT_NO_PAD socket option enabled and prioritize their patching; within 7 days, deploy the vendor-released patch across all affected Linux systems and coordinate necessary kernel reboots; within 30 days, confirm patch deployment completion and validate all systems are running patched kernel versions.
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