Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Zero rpc_gss_wire_cred at svcauth_gss_decode_credbody() entry svcauth_gss_decode_credbody() writes the caller's rpc_gss_wire_cred field by field and assigns gc_ctx.len only on the success tail. The caller storage is svcdata->clcred, which lives in the per-svc_rqst gss_svc_data and is reused across requests. Early decode failures leave partially decoded state mixed with residue from the prior request. The trailing body_len tightness check is the sharpest case: xdr_stream_decode_opaque_inline() has already written gc_ctx.data with a borrowed inline pointer into the current request's XDR pages, but gc_ctx.len retains its prior value. Once the request pages are released the pooled clcred carries a dangling pointer paired with a stale length. Zero the caller's rpc_gss_wire_cred at function entry so that every early-return path leaves a deterministic all-zero cred. On the trailing tightness-check path, gc_ctx.len is now zero instead of stale, which neuters length-driven consumers such as gss_svc_searchbyctx() that would otherwise walk the dangling data pointer.

Affected versions

Linux: b0bc53470d1af01f62a0fe2d405cf56477804863 through before 56b29d62017c7dd1718d060dd5b3a2ce61095d0c (git); b0bc53470d1af01f62a0fe2d405cf56477804863 through before 0e18641708eaa8bc3c1ff338cd844aeadbd52bac (git); b0bc53470d1af01f62a0fe2d405cf56477804863 through before e0778464049b0238f2915a40007a4154f86cf351 (git); b0bc53470d1af01f62a0fe2d405cf56477804863 through before 0fa8a8acae57e6373962741d5b06d13f44aba6a9 (git); b0bc53470d1af01f62a0fe2d405cf56477804863 through before 11539e8fcce0b0af062ae5fecf7b3676c2f7aeed (git); 6.3 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.