In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field<\/p>\n
gss_krb5_unwrap_v2() sets buf->len to a logical
\nlength, which can be much smaller than head[0].iov_len
\n(the allocated receive-page capacity). It then calls
\nxdr_buf_trim() with a trim length derived from the 16-bit
\n“extra count” (ec) field in the Kerberos v2 token header.<\/p>\n
The ec field is authenticated by the post-decrypt memcmp()
\nagainst the encrypted header copy, so a randomly-mutated
\nvalue is rejected. However, any peer holding a valid GSS
\ncontext can legitimately encrypt a token whose ec exceeds
\nthe plaintext length. Per RFC 4121, such a token is
\nstructurally malformed.<\/p>\n
Although xdr_buf_trim() now clamps the buf->len subtraction
\nto avoid unsigned underflow, the buffer is still left in a
\nsemantically invalid state (zero length, inconsistent iov
\nlengths) when ec is oversized.<\/p>\n
Reject these tokens before calling xdr_buf_trim(), giving
\ncallers a well-defined GSS_S_DEFECTIVE_TOKEN error and
\nkeeping the xdr_buf internally consistent. The wrapped blob
\nbegins at a nonzero offset — both callers pass len as
\noffset + opaque_len — so buf->len still counts the offset
\nbytes that precede the blob. Compare the trim length
\nagainst the remaining wrapped segment, buf->len – offset,
\nrather than the whole buffer; comparing against buf->len
\nalone leaves an offset-wide window in which an oversized ec
\npasses the test and xdr_buf_trim() cuts into the bytes ahead
\nof the blob.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field<\/p>\n
gss_krb5_unwrap_v2() sets buf->len to a logical
\nlength, which can be mu<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-21460","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/21460","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21460"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21460"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21460"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}