CVE-2026-89541
CVE-2026-89541 is a security vulnerability. O3 Security confirms whether CVE-2026-89541 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: harden gss_unwrap_resp_priv length checks gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length…
Description
In the Linux kernel, the following vulnerability has been resolved:
SUNRPC: harden gss_unwrap_resp_priv length checks
gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with
offset = (u8 *)(p) - (u8 *)head->iov_base;
if (offset + opaque_len > rcv_buf->len)
goto unwrap_failed;
maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset,
offset + opaque_len, rcv_buf);
Both operands are u32 and the sum is computed in u32. A reply with opaque_len near 0xffffffff makes offset + opaque_len wrap to a small value that is below rcv_buf->len, so the bound check passes and gss_unwrap() is called with end < begin. The check also lacks a lower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is accepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt header reads at ptr+4 and ptr+6 then run past the token.
A krb5p NFS server returning a crafted RPCSEC_GSS reply can drive the client into out-of-bounds reads in gss_krb5_unwrap_v2() and the rotate_left() loop that follows.
Fix by replacing the single combined check with three guards that are safe in u32 arithmetic and that enforce the RFC 4121 minimum outer token length:
if (offset > rcv_buf->len)
goto unwrap_failed;
if (opaque_len > rcv_buf->len - offset)
goto unwrap_failed;
if (opaque_len < GSS_KRB5_TOK_HDR_LEN)
goto unwrap_failed;
The first guard makes the subtraction in the second guard unconditionally safe; offset is derived from a successful xdr_inline_decode() in the head kvec, so in practice it already satisfies the bound. The floor mirrors the server-side check added in commit 5b757c2e57a5 ("SUNRPC: svcauth_gss: enforce krb5 token minimum length").
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-89541 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-89541 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-89541. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-89541 in your dependencies?
O3 detects CVE-2026-89541 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.