Description
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field gss_krb5_unwrap_v2() sets buf->len to a logical length, which can be much smaller than head[0].iov_len (the allocated receive-page capacity). It then calls xdr_buf_trim() with a trim length derived from the 16-bit "extra count" (ec) field in the Kerberos v2 token header. The ec field is authenticated by the post-decrypt memcmp() against the encrypted header copy, so a randomly-mutated value is rejected. However, any peer holding a valid GSS context can legitimately encrypt a token whose ec exceeds the plaintext length. Per RFC 4121, such a token is structurally malformed. Although xdr_buf_trim() now clamps the buf->len subtraction to avoid unsigned underflow, the buffer is still left in a semantically invalid state (zero length, inconsistent iov lengths) when ec is oversized. Reject these tokens before calling xdr_buf_trim(), giving callers a well-defined GSS_S_DEFECTIVE_TOKEN error and keeping the xdr_buf internally consistent. The wrapped blob begins at a nonzero offset -- both callers pass len as offset + opaque_len -- so buf->len still counts the offset bytes that precede the blob. Compare the trim length against the remaining wrapped segment, buf->len - offset, rather than the whole buffer; comparing against buf->len alone leaves an offset-wide window in which an oversized ec passes the test and xdr_buf_trim() cuts into the bytes ahead of the blob.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
cf4c024b908353fcc48309374d39e3399d67dfd1 to < ac9efc29346b6942e71f0e24a3178a9121330fabaffectedcf4c024b908353fcc48309374d39e3399d67dfd1 to < b5746095b59f4d11f39f08751d36bbdfd1e5deacaffectedcf4c024b908353fcc48309374d39e3399d67dfd1 to < 9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296affectedcf4c024b908353fcc48309374d39e3399d67dfd1 to < 4abb44a29bb515df6f49123848765c70fc9b5021affectedcf4c024b908353fcc48309374d39e3399d67dfd1 to < dfcd81ab45613d45996fbf483d4ef54b0ec90ab9affectedcf4c024b908353fcc48309374d39e3399d67dfd1 to < 1f9856af065b6158271687e9788407b9573fd16faffectedcf4c024b908353fcc48309374d39e3399d67dfd1 to < 880effc943ed82d6811f272ed3307c222b40f4d6affectedcf4c024b908353fcc48309374d39e3399d67dfd1 to < ad484748eec0a66eac0f13ab53b3fbedb7333c91affected
Linux Linux
Default version status: affected
3.13affected0 to < 3.13unaffected5.10.270 to ≤ 5.10.*unaffected5.15.221 to ≤ 5.15.*unaffected6.1.188 to ≤ 6.1.*unaffected6.6.157 to ≤ 6.6.*unaffected6.12.109 to ≤ 6.12.*unaffected6.18.50 to ≤ 6.18.*unaffected7.2.4 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/ac9efc29346b6942e71f0e24a3178a9121330fab ↗
- https://git.kernel.org/stable/c/b5746095b59f4d11f39f08751d36bbdfd1e5deac ↗
- https://git.kernel.org/stable/c/9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296 ↗
- https://git.kernel.org/stable/c/4abb44a29bb515df6f49123848765c70fc9b5021 ↗
- https://git.kernel.org/stable/c/dfcd81ab45613d45996fbf483d4ef54b0ec90ab9 ↗
- https://git.kernel.org/stable/c/1f9856af065b6158271687e9788407b9573fd16f ↗
- https://git.kernel.org/stable/c/880effc943ed82d6811f272ed3307c222b40f4d6 ↗
- https://git.kernel.org/stable/c/ad484748eec0a66eac0f13ab53b3fbedb7333c91 ↗