Synology-SA-19:33 HTTP/2 DoS Attacks

Abstract

CVE-2019-9511, CVE-2019-9513 and CVE-2019-9516 allow remote attackers to conduct denial-of-service attacks via a susceptible version of DiskStation Manager (DSM).

Affected Products

Mitigation

None

Detail

• CVE-2019-9511

  • Severity: Moderate
  • CVSS3 Base Score: 5.9
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  • Some HTTP/2 implementations are vulnerable to window size manipulation and stream prioritization manipulation, potentially leading to a denial of service. The attacker requests a large amount of data from a specified resource over multiple streams. They manipulate window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queued, this can consume excess CPU, memory, or both.

• CVE-2019-9512

  • Severity: Not affected
  • CVSS3 Base Score: 0.0
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:N
  • Some HTTP/2 implementations are vulnerable to ping floods, potentially leading to a denial of service. The attacker sends continual pings to an HTTP/2 peer, causing the peer to build an internal queue of responses. Depending on how efficiently this data is queued, this can consume excess CPU, memory, or both.

• CVE-2019-9513

  • Severity: Moderate
  • CVSS3 Base Score: 5.9
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  • Some HTTP/2 implementations are vulnerable to resource loops, potentially leading to a denial of service. The attacker creates multiple request streams and continually shuffles the priority of the streams in a way that causes substantial churn to the priority tree. This can consume excess CPU.

• CVE-2019-9514

  • Severity: Not affected
  • CVSS3 Base Score: 0.0
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:N
  • Some HTTP/2 implementations are vulnerable to a reset flood, potentially leading to a denial of service. The attacker opens a number of streams and sends an invalid request over each stream that should solicit a stream of RST_STREAM frames from the peer. Depending on how the peer queues the RST_STREAM frames, this can consume excess memory, CPU, or both.

• CVE-2019-9515

  • Severity: Not affected
  • CVSS3 Base Score: 0.0
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:N
  • Some HTTP/2 implementations are vulnerable to a settings flood, potentially leading to a denial of service. The attacker sends a stream of SETTINGS frames to the peer. Since the RFC requires that the peer reply with one acknowledgement per SETTINGS frame, an empty SETTINGS frame is almost equivalent in behavior to a ping. Depending on how efficiently this data is queued, this can consume excess CPU, memory, or both.

• CVE-2019-9516

  • Severity: Moderate
  • CVSS3 Base Score: 5.9
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  • Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.

• CVE-2019-9517

  • Severity: Not affected
  • CVSS3 Base Score: 0.0
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:N
  • Some HTTP/2 implementations are vulnerable to unconstrained interal data buffering, potentially leading to a denial of service. The attacker opens the HTTP/2 window so the peer can send without constraint; however, they leave the TCP window closed so the peer cannot actually write (many of) the bytes on the wire. The attacker then sends a stream of requests for a large response object. Depending on how the servers queue the responses, this can consume excess memory, CPU, or both.

• CVE-2019-9518

  • Severity: Not affected
  • CVSS3 Base Score: 0.0
  • CVSS3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:N
  • Some HTTP/2 implementations are vulnerable to a flood of empty frames, potentially leading to a denial of service. The attacker sends a stream of frames with an empty payload and without the end-of-stream flag. These frames can be DATA, HEADERS, CONTINUATION and/or PUSH_PROMISE. The peer spends time processing each frame disproportionate to attack bandwidth. This can consume excess CPU.

Reference

• HTTP/2 implementations do not robustly handle abnormal traffic and resource exhaustion
• CVE-2019-9511
• CVE-2019-9512
• CVE-2019-9513
• CVE-2019-9514
• CVE-2019-9515
• CVE-2019-9516
• CVE-2019-9517
• CVE-2019-9518

Revision